/Engine/Plugins/Online/OnlineSubsystem/Source/Public/Interfaces/OnlineFriendsInterface.h
Starts an async task that deletes a friend from the named friends list
true if the request was started successfully, false otherwise
bool DeleteFriend ( int32 LocalUserNum, const [FUniqueNetId](API\Runtime\CoreOnline\Online\FUniqueNetId) & FriendId, const [FString](API\Runtime\Core\Containers\FString) & ListName )